Forging heat treatment process for high-performance backing bearing outer ring

Abstract

The invention relates to the technical field of backing bearing outer rings, in particular to a forging heat treatment process of a high-performance backing bearing outer ring, which at least comprises the following steps: S1, smelting raw materials of the high-performance backing bearing outer ring, pouring, controlling the pouring temperature at 1500-1530 DEG C, and cooling to 500-560 DEG C to form a blank; s2, the blank is heated to 1150-1250 DEG C, and initial forging deformation is carried out through upsetting and drawing; s3, performing finish forging deformation at the finish forging temperature of 1050-1150 DEG C to obtain a forged piece; and S4, the forged piece is subjected to secondary forging back fire heat treatment. The specific forging heat treatment process is adopted, the grain and structure uniformity of the base body is improved, the obdurability of the base body is improved, the rolling requirement of the ultra-high-strength ultra-thin silicon steel of a silicon steel production line is met, the production efficiency is improved, the production cost is reduced, and good application prospects are achieved.

Description

Technical Field

[0001] The invention relates to the technical field of backing bearing outer rings, and in particular to a forging heat treatment process for a high-performance backing bearing outer ring. Background Art

[0002] The process of making bearing steel backing bearings covers smelting, pouring, billet forging, billet heat treatment after forging, outer ring forging, heat treatment after outer ring forging, final heat treatment and finishing. Among them, the billet forging and subsequent heat treatment steps have a significant impact on the grain size and organizational structure of the outer ring billet, which fundamentally determines the final strength, toughness, oxidation resistance and ability to resist thermal cracking of the outer ring.

[0003] However, the outer rings of currently imported backing bearings are mainly made of high-carbon chromium bearing steel, which has exposed a series of problems during use, such as high prices, long procurement cycles, relatively high failure rates, frequent cracking and peeling of the outer rings, and serious indentations on the roller surface. In contrast, the performance of domestically produced high-carbon chromium bearing steel backing bearings has not yet reached the level of imported products.

[0004] Chinese patent CN203412957U provides a backing bearing in a Sendzimir mill, which solves the technical problems of poor sealing performance of the backing bearing in the prior art; CN201908950U provides a backing bearing for a multi-roll mill, which improves the end face structure of the inner retaining ring, reduces the contact area between the inner retaining ring and the inner ring, and makes the contact end face between the inner retaining ring and the inner ring more fully lubricated. However, in the above-mentioned prior art, the outer ring material is high-carbon chromium bearing steel. In actual application, the outer ring of this material is prone to cracking and peeling, which cannot meet the rolling requirements of ultra-thin and ultra-high strength silicon steel sheets of the Sendzimir mill.

[0005] Therefore, it is of great significance to explore the failure mechanism of the outer ring of domestic high-carbon chromium bearing steel backing bearings and the improved technical solutions and processes to improve the performance of their blanks. Summary of the invention

[0006] In order to solve the problems in the prior art, the present invention provides a forging heat treatment process for a high-performance backing bearing outer ring, which at least includes the following steps:

[0007] S1. After melting, the raw material of the high-performance backing bearing outer ring is cast, the casting temperature is controlled at 1500-1530°C, and the cooling temperature is 500-560°C to form a blank;

[0008] S2, the billet is heated to 1150-1250℃ and subjected to initial forging deformation by upsetting and drawing;

[0009] S3, performing final forging deformation at a final forging temperature of 1050-1150°C to obtain a forging;

[0010] S4. Perform annealing heat treatment on the forgings after secondary forging.

[0011] In one embodiment, the chemical composition and weight percentage of the high performance backing bearing outer ring raw material include:

[0012] C: 0.98-1.5wt%, Si: 0.65-0.95wt%, Mn: 0.45-0.75wt%, P: <0.005wt%, S: <0. 003wt%, Cr: 2.5-4.5wt%, Mo: 0.5-0.85wt%, W: 0.3-0.5wt%, N: 0.12-0.25wt%.

[0013] In a preferred embodiment, the content of the C element is any one of 0.99wt%, 1.1wt%, 1.2wt%, 1.3wt% and 1.5wt%.

[0014] In a preferred embodiment, the content of the Si element is any one of 0.69wt%, 0.75wt%, 0.8wt%, 0.9wt% and 0.95wt%.

[0015] In a preferred embodiment, the content of the Mn element is any one of 0.48wt%, 0.55wt%, 0.6wt%, 0.65wt%, and 0.75wt%.

[0016] In a preferred embodiment, the content of the P element is 0.015 wt %.

[0017] In a preferred embodiment, the content of the S element is 0.008 wt %.

[0018] In a preferred embodiment, the content of the Cr element is any one of 2.6wt%, 3wt%, 3.5wt%, 4.3wt% and 4.5wt%.

[0019] In a preferred embodiment, the content of the Mo element is any one of 0.58wt%, 0.65wt%, 0.7wt%, 0.07wt%, 0.8wt% and 0.85wt%.

[0020] In a preferred embodiment, the content of the W element is any one of 0.32wt%, 0.4wt%, 0.45wt%, 0.48wt% and 0.5wt%.

[0021] In a preferred embodiment, the content of the N element is any one of 0.12wt%, 0.15wt%, 0.18wt%, 0.03wt%, 0.2wt%, and 0.25wt%.

[0022] In one embodiment, the material of the outer ring of the high-performance backing bearing is GCr18Mo.

[0023] In a preferred embodiment, the pouring temperature in step S1 is any one of 1500°C, 1510°C, 1520°C, 1525°C, and 1530°C.

[0024] In a preferred embodiment, the cooling temperature in step S1 is any one of 500°C, 520°C, 540°C, 550°C, and 560°C.

[0025] In one embodiment, the billet heating process in step S2 is: heating to 850°C at a heating rate of <80°C / h, keeping the temperature for 1h, and then heating to 1150-1250°C at a heating rate of 180-200°C / h.

[0026] In a preferred embodiment, the heating rate is any one of 180°C / h, 185°C / h, 190°C / h, and 200°C / h.

[0027] In a preferred embodiment, the temperature of the initial forging deformation in step S2 is any one of 1150°C, 1180°C, 1200°C, 1220°C, and 1250°C.

[0028] In one embodiment, the upsetting is performed 2-3 times, and the stretching is performed 2-3 times.

[0029] In one embodiment, the forging ratio of the initial forging deformation is greater than 5.

[0030] In a preferred embodiment, the forging ratio of the initial forging deformation is any one of 5, 5.5, 6, 6.2, and 6.5.

[0031] When forging the outer ring blank of the backing bearing, the forging ratio is controlled above 5. After cooling, the forging can obtain fine and uniform grains, which provides a good original grain structure for the heat treatment process and also lays the foundation for the forging to obtain qualified mechanical properties.

[0032] In one embodiment, the deformation amount of the upsetting is controlled at 35-55.

[0033] In a preferred embodiment, the deformation amount of the upsetting is any one of 35%, 40%, 50%, 52%, and 55%.

[0034] In one embodiment, the stretching is performed by a wide anvil strong pressing method, and the pressing amount of each anvil is controlled at 20-30%.

[0035] In a preferred embodiment, the compression amount of each anvil is any one of 20%, 22%, 26%, 28%, and 30%.

[0036] In one embodiment, the final forging temperature in step S3 is any one of 1050°C, 1080°C, 1100°C, 1120°C, and 1150°C.

[0037] In one embodiment, the final forging deformation in step S3 is 15-20%.

[0038] In a preferred embodiment, the final forging deformation in step S3 is any one of 15%, 16%, 17%, 18%, and 20%.

[0039] In one embodiment, the S4 step comprises:

[0040] a. The forging obtained after step S3 is air-cooled, the surface temperature of the forged shaft is reduced to 860-980°C for normalizing, and then put into the furnace for heat preservation for 4-8 hours;

[0041] b. After the heat preservation is completed, the furnace is cooled to 620-640℃ for tempering and the temperature is kept for 8-12h;

[0042] c. Cool the forging after being processed in step b.

[0043] In one embodiment, the step c is specifically as follows: after the forging processed in step b is kept warm, it is cooled at a cooling rate of ≤20°C / h, and when the furnace temperature is ≤200°C, it is taken out of the furnace and cooled to room temperature.

[0044] In one embodiment, the grain size of the forging after the S4 step is 6.5-7.0.

[0045] After the forging heat treatment process of the present application, the forgings obtain fine and uniform grains, which provides a good organizational basis for the final heat treatment. This is because the grains are fine after forging heat treatment, there are more grain boundaries in a certain volume, the resistance to dislocation movement increases, the yield strength increases, and the effect of grain boundary strengthening is played. Secondly, the interface hinders the movement of microcracks, and the microcrack propagation speed is restricted. At the same time, the grain boundary area increases, the inclusions produced by segregation on the grain boundary are relatively reduced, the grain boundary bonding force is improved, and the plasticity is increased. The finer the grains, the more grain boundaries there are in a unit volume, the more grains participate in deformation, and the more uniform the deformation, so that it undergoes greater plastic deformation before fracture. Strength and plasticity increase at the same time, and the metal consumes more energy before fracture, so its toughness is also improved.

[0046] Beneficial Effects

[0047] 1. Based on the system of the present invention, during the forging production of the backing bearing outer ring blank, the forging ratio is controlled to be above 5, and the forging obtains fine and uniform grains after cooling, which provides a good original grain structure for the heat treatment process and also lays a foundation for the forging to obtain qualified mechanical properties.

[0048] 2. Based on the system of the present invention, an innovative secondary post-forging annealing heat treatment process is adopted to eliminate the internal stress of the forging and the mixed crystal phenomenon of uneven grain size. The first annealing improves the forging blank structure, and the second annealing improves the forging blank mechanical properties, ensuring the mechanical property requirements of the backing bearing blank, and can further solve the problems of the outer ring of the high-carbon chromium bearing steel backing bearing during use, such as cracking, short service life and frequent peeling, so as to improve production efficiency and reduce production costs.

[0049] 3. In the present invention, by increasing the forging ratio, increasing the number of upsetting and drawing, and appropriately optimizing and controlling the final forging temperature, the rolling performance stability of the designed backing bearing outer ring during its service life on the machine is improved, meeting the rolling requirements of ultra-high strength and ultra-thin silicon steel products. At the same time, the rolling mileage of a single machine is increased by 20% compared with the rolling mileage of the original material.

[0050] 4. The backing bearing outer ring working layer developed by the present invention using a specific forging heat treatment process has a stable and consistent microstructure control, a small hardness drop, and a hardness drop of only about 1HSD in a single-side working layer.

[0051] 5. The present invention adopts a specific forging and post-forging heat treatment process design. After forging, the outer ring of the backing bearing has a tensile strength of 1260-1320 MPa at room temperature, an impact energy of AKV2 of 40-50 J, and a hardness of HRC of 45-50. DETAILED DESCRIPTION

[0052] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0053] Example 1

[0054] This embodiment provides a forging heat treatment process for a high-performance backing bearing outer ring, which at least includes the following steps:

[0055] S1. The high-performance backing bearing outer ring raw material is melted and then cast. The casting temperature is controlled at 1500°C and the cooling temperature is 500°C to form a blank.

[0056] S2, the billet is heated to 850°C at a heating rate of 75°C / h, kept at that temperature for 1h, and then heated to 1150°C at a heating rate of 180°C / h for initial forging deformation;

[0057] S3, performing final forging deformation at a final forging temperature of 1050° C. to obtain a forging;

[0058] S4. Perform annealing heat treatment on the forgings after secondary forging.

[0059] The chemical composition and weight percentage of the high performance backing bearing outer ring raw material include:

[0060] C: 0.99wt%, Si: 0.69wt%, Mn: 0.48wt%, P: 0.015wt%, S: 0.008wt%, Cr: 2.6wt%, Mo: 0.58wt%, W: 0.32wt%, N: 0.12wt%, and the balance is Fe.

[0061] The upsetting times are 2 times, and the stretching times are 2 times.

[0062] The forging ratio of the initial forging deformation is 5.

[0063] The deformation amount of the upsetting is 35%.

[0064] The stretching is performed by a wide anvil strong pressure method, and the pressing amount of each anvil is controlled at 20%.

[0065] The final forging deformation in the step S3 is 15%.

[0066] The S4 step includes:

[0067] a. The forging obtained after step S3 is air-cooled, the surface temperature of the forged shaft is reduced to 860°C for normalizing, and then put into the furnace for heat preservation for 6 hours;

[0068] b. After the insulation is completed, cool the furnace to 630℃ for tempering and keep it warm for 10 hours.

[0069] c. Keep the forging treated in step b warm and then cool it at a cooling rate of 20°C / h until the furnace temperature reaches 200°C, then take it out of the furnace and cool it to room temperature.

[0070] Example 2

[0071] This embodiment provides a forging heat treatment process for a high-performance backing bearing outer ring, which at least includes the following steps:

[0072] S1. The high-performance backing bearing outer ring raw material is melted and then cast. The casting temperature is controlled at 1510°C and the cooling temperature is 520°C to form a blank.

[0073] S2, the billet is heated to 850°C at a heating rate of 75°C / h, kept at that temperature for 1h, and then heated to 1180°C at a heating rate of 185°C / h for initial forging deformation;

[0074] S3, performing final forging deformation at a final forging temperature of 1080° C. to obtain a forging;

[0075] S4. Perform annealing heat treatment on the forgings after secondary forging.

[0076] The chemical composition and weight percentage of the high performance backing bearing outer ring raw material include:

[0077] C: 1.1wt%, Si: 0.75wt%, Mn: 0.55wt%, P: 0.015wt%, S: 0.008wt%, Cr: 3wt%, Mo: 0.65wt%, W: 0.4wt%, N: 0.15wt%, and the balance is Fe.

[0078] The upsetting times are 2 times, and the stretching times are 2 times.

[0079] The forging ratio of the initial forging deformation is 5.5.

[0080] The deformation amount of the upsetting is 40%.

[0081] The drawing is carried out by a wide anvil strong pressure method, and the pressing amount of each anvil is controlled at 22%.

[0082] The final forging deformation in the step S3 is 16%.

[0083] The S4 step includes:

[0084] a. The forging obtained after step S3 is air-cooled, the surface temperature of the forged shaft is reduced to 860°C for normalizing, and then put into the furnace for heat preservation for 6 hours;

[0085] b. After the insulation is completed, cool the furnace to 630℃ for tempering and keep it warm for 10 hours.

[0086] c. Keep the forging treated in step b warm and then cool it at a cooling rate of 20°C / h until the furnace temperature reaches 200°C, then take it out of the furnace and cool it to room temperature.

[0087] Example 3

[0088] This embodiment provides a forging heat treatment process for a high-performance backing bearing outer ring, which at least includes the following steps:

[0089] S1. The high-performance backing bearing outer ring raw material is smelted and then cast. The casting temperature is controlled at 1520°C and the cooling temperature is 540°C to form a blank.

[0090] S2, the billet is heated to 850°C at a heating rate of 75°C / h, kept at this temperature for 1h, and then heated to 1200°C at a heating rate of 190°C / h for initial forging deformation;

[0091] S3, performing final forging deformation at a final forging temperature of 1100° C. to obtain a forging;

[0092] S4. Perform annealing heat treatment on the forgings after secondary forging.

[0093] The chemical composition and weight percentage of the high performance backing bearing outer ring raw material include:

[0094] C: 1.2wt%, Si: 0.8wt%, Mn: 0.6wt%, P: 0.015wt%, S: 0.008wt%, Cr: 3.5wt%, Mo: 0.7wt%, W: 0.45wt%, N: 0.18wt%, and the balance is Fe.

[0095] The upsetting times are 3 times, and the stretching times are 3 times.

[0096] The forging ratio of the initial forging deformation is 6.

[0097] The deformation amount of the upsetting is 50%.

[0098] The drawing is carried out by a wide anvil strong pressure method, and the pressing amount of each anvil is controlled at 26%.

[0099] The final forging deformation in the step S3 is 17%.

[0100] The S4 step includes:

[0101] a. The forging obtained after step S3 is air-cooled, the surface temperature of the forged shaft is reduced to 860°C for normalizing, and then put into the furnace for heat preservation for 6 hours;

[0102] b. After the insulation is completed, cool the furnace to 630℃ for tempering and keep it warm for 10 hours.

[0103] c. Keep the forging treated in step b warm and then cool it at a cooling rate of 20°C / h until the furnace temperature reaches 200°C, then take it out of the furnace and cool it to room temperature.

[0104] Example 4

[0105] This embodiment provides a forging heat treatment process for a high-performance backing bearing outer ring, which at least includes the following steps:

[0106] S1. The high-performance backing bearing outer ring raw material is melted and then cast. The casting temperature is controlled at 1525°C and the cooling temperature is 550°C to form a blank.

[0107] S2, the billet is heated to 850°C at a heating rate of 75°C / h, kept at that temperature for 1h, and then heated to 1220°C at a heating rate of 185°C / h for initial forging deformation;

[0108] S3, performing final forging deformation at a final forging temperature of 1120° C. to obtain a forging;

[0109] S4. Perform annealing heat treatment on the forgings after secondary forging.

[0110] The chemical composition and weight percentage of the high performance backing bearing outer ring raw material include:

[0111] C: 1.3wt%, Si: 0.9wt%, Mn: 0.65wt%, P: 0.015wt%, S: 0.008wt%, Cr: 4.3wt%, Mo: 0.8wt%, W: 0.48wt%, N: 0.2wt%, and the balance is Fe.

[0112] The upsetting times are 3 times, and the stretching times are 3 times.

[0113] The forging ratio of the initial forging deformation is 6.2.

[0114] The deformation amount of the upsetting is 52%.

[0115] The drawing is carried out by a wide anvil strong pressure method, and the pressing amount of each anvil is controlled at 28%.

[0116] The final forging deformation in the step S3 is 18%.

[0117] The S4 step includes:

[0118] a. The forging obtained after step S3 is air-cooled, the surface temperature of the forged shaft is reduced to 860°C for normalizing, and then put into the furnace for heat preservation for 6 hours;

[0119] b. After the insulation is completed, cool the furnace to 630℃ for tempering and keep it warm for 10 hours.

[0120] c. Keep the forging treated in step b warm and then cool it at a cooling rate of 20°C / h until the furnace temperature reaches 200°C, then take it out of the furnace and cool it to room temperature.

[0121] Example 5

[0122] This embodiment provides a forging heat treatment process for a high-performance backing bearing outer ring, which at least includes the following steps:

[0123] S1. The high-performance backing bearing outer ring raw material is melted and then cast. The casting temperature is controlled at 1530°C and the cooling temperature is 560°C to form a blank.

[0124] S2, the billet is heated to 850°C at a heating rate of 75°C / h, kept at that temperature for 1h, and then heated to 1250°C at a heating rate of 200°C / h for initial forging deformation;

[0125] S3, performing final forging deformation at a final forging temperature of 1150° C. to obtain a forging;

[0126] S4. Perform annealing heat treatment on the forgings after secondary forging.

[0127] The chemical composition and weight percentage of the high performance backing bearing outer ring raw material include:

[0128] C: 1.5wt%, Si: 0.95wt%, Mn: 0.75wt%, P: 0.015wt%, S: 0.008wt%, Cr: 4.5wt%, Mo: 0.85wt%, W: 0.5wt%, N: 0.25wt%, and the balance is Fe.

[0129] The upsetting times are 3 times, and the stretching times are 3 times.

[0130] The forging ratio of the initial forging deformation is 6.5.

[0131] The deformation amount of the upsetting is 55%.

[0132] The drawing is carried out by a wide anvil strong pressure method, and the pressing amount of each anvil is controlled at 30%.

[0133] The final forging deformation in the step S3 is 20%.

[0134] The S4 step includes:

[0135] a. The forging obtained after step S3 is air-cooled, the surface temperature of the forged shaft is reduced to 860°C for normalizing, and then put into the furnace for heat preservation for 6 hours;

[0136] b. After the insulation is completed, cool the furnace to 630℃ for tempering and keep it warm for 10 hours.

[0137] c. Keep the forging treated in step b warm and then cool it at a cooling rate of 20°C / h until the furnace temperature reaches 200°C, then take it out of the furnace and cool it to room temperature.

[0138] Performance Testing

[0139] 1. Room temperature mechanical properties test: According to GB / T 13313 roller Shore and Leeb hardness test method and GB / T228.1-2010 metal material tensile test Part 1: room temperature tensile test method, the high performance backing bearing outer ring prepared in Examples 1-5 and the original backing bearing outer ring (KOYO bearing) were tested for room temperature mechanical properties. The test results are shown in Table 1.

[0140] 2. Test of average rolling mileage on a single machine: The high-performance backing bearing outer ring prepared in Example 5 and the original backing bearing outer ring were tested. The test results are shown in Table 2.

[0141] Table 1

[0142] <![CDATA[R m / MPa]]> <![CDATA[A KU2 / J]]> HRC Example 1 1260 40 45.0 Example 2 1280 42 43.5 Example 3 1290 45 45.0 Example 4 1300 47 48.5 Example 5 1320 50 50.0 Original backing bearing outer ring 1180-1230 30-40 40-46

[0143] Table 2

[0144] sample Average rolling mileage per slot per machine / km Example 5 10800 Original backing bearing outer ring 9000

[0145] As shown in Table 1-2, the outer ring of the backing bearing in Example 1-5 has a tensile strength of 1260-1320 MPa at room temperature and an impact energy of A KV2 The hardness is 40-50J and the HRC hardness is 45-50.

[0146] The backing bearing outer ring prepared by the present invention, after the same final heat treatment process, has an average rolling mileage of 10800 km per machine, which is 20% higher than the average rolling mileage of 9000 km per machine of the original backing bearing outer ring.

Claims

1. A forging heat treatment process for a high-performance backing bearing outer ring, characterized in that: At least the following steps are included: S1. After melting, the raw material of the high-performance backing bearing outer ring is cast, the casting temperature is controlled at 1500-1530°C, and the cooling temperature is 500-560°C to form a blank; S2, the billet is heated to 1150-1250℃ and subjected to initial forging deformation by upsetting and drawing; S3, performing final forging deformation at a final forging temperature of 1050-1150°C to obtain a forging; S4. Perform annealing heat treatment on the forgings after secondary forging.

2. The forging heat treatment process of the high-performance backing bearing outer ring according to claim 1 is characterized in that: The chemical composition and weight percentage of the high performance backing bearing outer ring raw material include: C: 0.98-1.5wt%, Si: 0.65-0.95wt%, Mn: 0.45-0.75wt%, P: <0.005wt%, S: <0. 003wt%, Cr: 2.5-4.5wt%, Mo: 0.5-0.85wt%, W: 0.3-0.5wt%, N: 0.12-0.25wt%.

3. The forging heat treatment process for the outer ring of the high-performance backing bearing according to claim 1 is characterized in that: The billet heating process in step S2 is as follows: heating to 850°C at a heating rate of <80°C / h, keeping the temperature for 1h, and then heating to 1150-1250°C at a heating rate of 180-200°C / h.

4. The forging heat treatment process for the outer ring of the high-performance backing bearing according to claim 1 is characterized in that: The upsetting times are 2-3 times, and the stretching times are 2-3 times.

5. The forging heat treatment process for the outer ring of the high-performance backing bearing according to claim 4 is characterized in that: The forging ratio of the initial forging deformation is greater than 5.

6. The forging heat treatment process for the outer ring of the high-performance backing bearing according to claim 4 is characterized in that: The deformation amount of the upsetting is controlled at 35-55%.

7. The forging heat treatment process for the outer ring of the high-performance backing bearing according to claim 4 is characterized in that: The stretching is performed by a wide anvil strong pressure method, and the pressing amount of each anvil is controlled at 20-30%.

8. The forging heat treatment process for the outer ring of the high-performance backing bearing according to claim 1 is characterized in that: The final forging deformation in step S3 is 15-20%.

9. The forging heat treatment process for the outer ring of the high-performance backing bearing according to claim 1 is characterized in that: The S4 step includes: a. The forging obtained after step S3 is air-cooled, the surface temperature of the forged shaft is reduced to 860-980°C for normalizing, and then put into the furnace for heat preservation for 4-8 hours; b. After the heat preservation is completed, the furnace is cooled to 620-640℃ for tempering and the temperature is kept for 8-12h; c. Cool the forging after being processed in step b.

10. The forging heat treatment process for the outer ring of the high-performance backing bearing according to claim 9, characterized in that: The step c is specifically as follows: keeping the forging treated in step b warm and then cooling it at a cooling rate of ≤20°C / h, taking it out of the furnace when the furnace temperature is ≤200°C and cooling it to room temperature.